Here are some examples of theories which I have decided, after long thought and using no science whatsoever, are completely wrong.
1. The MultiverseThe multiverse is a very cool, intriguing idea that everyone loves but it just doesn't stand up. The idea is that there are an infinite number of universes, with an infinite number of possibilities. Which immediately raises the stock response, that an infinite number of universes and possibilities must include one where the multiverse doesn't exist. Plus, like, doesn't "the universe" mean "everything"? So if there are multiple universes aren't they all just part of "the universe"?
One of the theories around the multiverse is that the universe splits every time two or more possibilities exist. In simple (and probably wrong) terms, one example could be every time you make a decision. So if you turned down a job, or decided not to move to another country, then another universe exists where you accepted that job or moved to that country. Or another universe exists where JFK wasn't assassinated, Hitler drowned as a toddler, or the US didn't invade Iraq. You can see the immediate appeal of such a theory, and I don't think immensely clever theoretical physicists are any more immune to "what if" fantasies than the rest of us.
The problem with this idea is that it gets ridiculous pretty fast. More than one possibility exists all the time. So if I have cereal instead of toast this morning, or my cat jumps right instead of left, the universe splits and another me and another cat, pursue their different lives. And along with us, we take all our family members and furniture and casual acquaintances with us. But why? To what end? In the end this theory just doesn't make any sense.
In my favourite bit from Futurama (episode: I Dated A Robot), Fry travels to the edge of the universe and sees alternate versions of himself and his friends looking back at them.
Fry: Far out! So there really is an infinate number of universes?
Professor Farnsworth: No, just the two.
2. The Theory of EverythingScientists have been searching for a unifying theory that will explain the universe and reconcile general relativity and quantum mechanics, many convinced that such a single, unifying explanation of all things must exist. And what has been the best suggestion to date? String theory. The universe is made up of tiny vibrating strings and mini-universes. (I might have that a bit wrong).
I think this is a limitation of our brains - we love "truth in beauty", we love balance and harmony and we don't like loose ends. Is that a sign that the universe is the same? Or just a side effect of our wiring which has served us well in our evolutionary history?
Who says all the workings of the universe have to be unified? It's a natural assumption, and one I guess we all secretly believe (me as well). But actually it seems not to be the case. Why should it be the case? No one can really come up with a reason, other than appealing to logic and "elegance" or "beauty" which may really be things that our logical, orderly minds require more than actual physical laws.
I actually think that searching for a unifying theory of everything is the equivalent of believing in a God.